U.S. patent number 5,779,731 [Application Number 08/770,875] was granted by the patent office on 1998-07-14 for balloon catheter having dual markers and method.
This patent grant is currently assigned to Cordis Corporation. Invention is credited to Ernest E. Leavitt.
United States Patent |
5,779,731 |
Leavitt |
July 14, 1998 |
Balloon catheter having dual markers and method
Abstract
An intravascular balloon catheter has a balloon near the distal
end of a catheter shaft and a pair of radiopaque markers positioned
within the balloon interior. The distal marker is disposed on an
inner shaft member, and the proximal marker is disposed at the
distal end of an outer shaft member. The markers may be positioned
to indicate under fluoroscopy the position and working length of
the balloon.
Inventors: |
Leavitt; Ernest E. (Coral
Springs, FL) |
Assignee: |
Cordis Corporation (Miami,
FL)
|
Family
ID: |
25089973 |
Appl.
No.: |
08/770,875 |
Filed: |
December 20, 1996 |
Current U.S.
Class: |
606/194;
604/103.1; 606/198 |
Current CPC
Class: |
A61M
25/0108 (20130101); A61M 2025/1079 (20130101); A61M
25/1027 (20130101) |
Current International
Class: |
A61M
25/01 (20060101); A61M 25/00 (20060101); A61M
029/00 () |
Field of
Search: |
;606/191,192,194,195,198,200 ;604/95-101 ;623/1,12 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Buiz; Michael
Assistant Examiner: Lewis; William W.
Attorney, Agent or Firm: Montgomery; Michael W.
Claims
I claim:
1. An intravascular balloon catheter for treating a portion of the
body of a patient, comprising:
a flexible catheter shaft, at least a distal portion of the
catheter shaft having an inner shaft member coaxially surrounded by
an outer shaft member, an inflation lumen being defined by an
annular space between said inner and outer shaft members;
a flexible balloon disposed near a distal end of the catheter
shaft, the balloon having a working portion with a constant
cross-sectional area, a proximal end of the balloon being sealed to
the outer shaft member, and a distal end of the balloon being
sealed to the inner shaft member, whereby the inflation lumen is in
fluid communication with the interior of the balloon; and
first and second radiopaque markers disposed within the interior of
the balloon, the first marker being affixed to the inner shaft
member, and the second marker being affixed to the outer shaft
member, said first and second markers being positioned at a distal
and proximal end of the balloon working portion, respectively,
whereby the first and second markers indicate under fluoroscopy the
position of the balloon working portion within the body of the
patient.
2. The intravascular balloon catheter as set forth in claim 1,
wherein the balloon working portion has a cylindrical shape.
3. The intravascular balloon catheter as set forth in claim 2, the
balloon further comprising a proximal and distal frusto-conical
tapering segment, and proximal and distal legs being sealed to the
outer and inner shaft members, respectively, wherein each of the
first and second markers are longitudinally positioned at a
transition between the cylindrical working portion and the distal
and proximal tapering segments, respectively.
4. The intravascular balloon catheter as set forth in claim 1,
wherein the balloon is formed of at least two layers of different
materials.
5. The intravascular balloon catheter as set forth in claim 1,
further comprising a flexible fixed wire affixed to the inner shaft
member and extending distally beyond the distal end of the inner
shaft member.
6. The intravascular balloon catheter as set forth in claim 1,
wherein the balloon is formed of a substantially inelastic
material.
7. The intravascular balloon catheter as set forth in claim 1,
wherein the inner shaft member defines a guidewire lumen adapted to
slidingly receive a guidewire extending from a proximal guidewire
port that is proximal of the balloon to a distal guidewire port
that is distal to the balloon.
8. The intravascular balloon catheter as set forth in claim 7,
wherein the proximal guidewire port is disposed between a proximal
end of the catheter shaft and the balloon, thereby enabling a
guidewire to traverse a path from the distal guidewire port through
the guidewire lumen defined by the inner shaft member, through the
proximal guidewire port, and extend proximally along the exterior
of a proximal portion of the catheter shaft in a rapid exchange
configuration.
9. The intravascular balloon catheter as set forth in claim 7,
wherein said catheter shaft further comprises a proximal shaft
portion defining a proximal inflation lumen and a proximal
guidewire lumen, the proximal inflation lumen communicating with an
inflation lumen defined by an annular space between the outer and
inner shaft members, and the proximal guidewire lumen extending
parallel to the proximal inflation lumen and communicating with the
guidewire lumen.
10. The intravascular balloon catheter as set forth in claim 7,
wherein said inner shaft member is formed of at least two layers of
different materials, the innermost layer defining the guidewire
lumen and being more lubricious to facilitate movement of a
guidewire within the guidewire lumen.
11. The intravascular balloon catheter as set forth in claim 1,
wherein inner and outer shaft members are each formed of plastic,
and the first and second markers are formed of metal.
12. An intravascular balloon catheter for treating a portion of the
body of a patient, comprising:
a flexible catheter shaft. at least a distal portion of the
catheter shaft having an inner shaft member coaxially surrounded by
an outer shaft member, an inflation lumen being defined by an
annular space between said inner and outer shaft members;
a flexible balloon disposed near a distal end of the catheter
shaft, a proximal end of the balloon being sealed to the outer
shaft member, and a distal end of the balloon being sealed to the
inner shaft member, whereby the inflation lumen is in fluid
communication with the interior of the balloon; and
first and second radiopaque markers disposed within the interior of
the balloon, the first marker being affixed to the inner shaft
member, and the second marker being affixed to the outer shaft
member, whereby the first and second markers indicate under
fluoroscopy the position of the balloon within the body of the
patient, wherein the second marker is formed by a plastic ring
containing a radiopaque agent and affixed to a distal end of said
outer shaft member.
13. The intravascular balloon catheter as set forth in claim 12,
wherein a percentage concentration of said radiopaque agent is
predetermined, such that said first and second markers have equal
fluoroscopic brightness.
14. The intravascular balloon catheter as set forth in claim 12,
wherein the second marker has the same outer diameter as said outer
shaft member.
15. An intravascular balloon catheter, comprising:
a first tube of flexible plastic defining a guidewire lumen, said
first tube being formed of an outer plastic layer and an inner
plastic layer, the plastic materials of said outer and inner
plastic layers being different and bonded to each other, said
guidewire lumen being adapted to slidingly receive a guidewire,
said inner plastic layer exhibiting a more lubricious surface than
said outer plastic layer;
a second flexible plastic tube surrounding said first tube and
defining an inflation lumen between the outer surface of the first
tube and the inner surface of the second tube;
a flexible balloon having a distal end coupled to said first tube
and a proximal end coupled to said second tube, such that the
interior volume of the balloon is in fluid communication with said
inflation lumen; and
first and second radiopaque markers affixed to the first and second
tube, respectively.
16. The intravascular balloon catheter as set forth in claim 15, in
which the material of the outer plastic layer has greater stiffness
than the material of the inner plastic layer.
17. The intravascular balloon catheter as set forth in claim 15, in
which the material of said outer plastic layer is selected from the
group consisting of nylon, polyurethane, and polyester.
18. The intravascular balloon catheter as set forth in claim 15,
wherein the balloon defines a working length, said first and second
markers being positioned at a distal and proximal end of the
working length, respectively.
19. The intravascular balloon catheter as set forth in claim 15,
wherein the balloon is formed of a substantially inelastic
material.
20. The intravascular balloon catheter as set forth in claim 15,
further comprising a distal guidewire port that is distal to the
balloon and a proximal guidewire port that is between the balloon
and a proximal end of the second tube, thereby enabling a guidewire
to traverse a path from the distal guidewire port through the
guidewire lumen, through the proximal guidewire port, and extend
proximally along the exterior of a proximal portion of the catheter
shaft in a rapid exchange configuration.
21. The intravascular balloon catheter as set forth in claim 20,
wherein the second marker has the same outer diameter as said
second shaft member.
22. The intravascular balloon catheter as set forth in claim 15,
wherein the second marker is formed by a plastic ring containing a
radiopaque agent and affixed to a distal end of said second shaft
member.
23. The intravascular balloon catheter as set forth in claim 15,
wherein inner and outer shaft members are each formed of plastic,
and the first and second markers are formed of metal.
24. An intravascular balloon catheter for expanding a stent within
the body of a patient, comprising:
a flexible catheter shaft, at least a distal portion of the
catheter shaft having an inner shaft member coaxially surrounded by
an outer shaft member;
a flexible balloon disposed near a distal end of the catheter
shaft, a proximal end of the balloon being sealed to the outer
shaft member, and a distal end of the balloon being sealed to the
inner shaft member;
first and second radiopaque markers disposed within the interior of
the balloon, the first marker being affixed to the inner shaft
member, and the second marker being affixed to a distal end of the
outer shaft member, an outer diameter of the second inner marker
being larger than an outer diameter of the outer shaft member,
thereby forming an annular shelf;
a stent assembled in a crimped configuration around the balloon in
an uninflated state, whereby the balloon is adapted to inflate and
expand the stent within the desired site, said annular shelf
engaging a proximal end of the stent to resist proximal motion of
the stent relative to the catheter shaft as the balloon catheter is
advanced within the body of the patient.
25. The intravascular balloon catheter as set forth in claim 24,
wherein the balloon defines a working length, said first and second
markers being positioned at a distal and proximal end of the
working length, respectively.
26. The intravascular balloon catheter as set forth in claim 24,
wherein the inner shaft member defines a guidewire lumen adapted to
slidingly receive a guidewire extending from a proximal guidewire
port that is proximal of the balloon to a distal guidewire port
that is distal to the balloon.
27. The intravascular balloon catheter as set forth in claim 26,
wherein the proximal guidewire port is disposed between a proximal
end of the catheter shaft and the balloon, thereby enabling a
guidewire to traverse a path from the distal guidewire port through
the guidewire lumen defined by the inner shaft member, through the
proximal guidewire port, and extend proximally along the exterior
of a proximal portion of the catheter shaft in a rapid exchange
configuration.
28. A method of making an intravascular balloon catheter for
treating a portion of the body of a patient, comprising the steps
of:
providing an outer and inner shaft member, the outer shaft member
being a tube defining a lumen having an inner diameter that is
large enough to accept the inner shaft member within said
lumen;
affixing distal and proximal radiopaque markers to the inner and
outer shaft members, respectively;
providing a flexible balloon having a central substantially
cylindrical portion, and a proximal and distal tapering
segment;
sealing a proximal end of the balloon to the outer shaft member,
such that the proximal marker is longitudinally aligned with a
proximal transition between the central portion and the proximal
tapering segment;
inserting the inner shaft member within the lumen of the outer
shaft member and longitudinally aligning the distal marker with a
distal transition between the central portion and the distal
tapering segment; and
sealing a distal end of the balloon to the inner shaft member while
the distal marker and the distal transition are so aligned.
29. The method of claim 28, further comprising the additional step
of sealing the proximal ends of the inner and outer shaft members,
to resist relative movement thereof.
30. The method of claim 28, further comprising the additional step
of forming the proximal marker of a plastic formulation having a
radiopaque agent.
31. The method of claim 28, wherein said step of providing the
inner shaft member further comprises coextruding the inner shaft
member into a tube defining a lubricious guidewire lumen.
Description
BACKGROUND AND DESCRIPTION OF THE INVENTION
This invention relates generally to the field of intravascular
catheters, and more particularly to a balloon catheter having dual
markers.
Intravascular catheters for advancement into the blood vessels of a
patient are presently in wide clinical use. Many clinical
applications exist for such catheters, including diagnostic and
interventional procedures. Diagnostic procedures include
angiography, in which a catheter is advanced along a selected
vascular path until a distal tip of the catheter is located at the
desired site. A liquid dye is then injected from a proximal hub
outside the patient's body, through an infusion lumen, and out the
catheter distal tip. This dye is radiopaque, so that its flow
through the blood vessels can be visualized on a fluoroscopy
system.
Interventional procedures include any treatment or therapy, as
opposed to diagnosis, using an intravascular catheter having an
interventional device to cause a change in the blood vessel. The
most common interventional device is a dilatation balloon, which
can be expanded within a narrowing or obstruction of a blood vessel
or other body passageway to increase blood flow or otherwise treat
the diseased region. One advantage of using a balloon catheter to
treat an area of a patient's vascular system is to avoid the
difficulties associated with performing surgery.
For example, in a typical balloon angioplasty procedure, a
partially or fully occluded blood vessel lumen is enlarged and
reopened to allow greater blood flow. A balloon catheter is
introduced percutaneously into the vascular system and advanced
along the desired path until the balloon reaches the site of the
obstruction or constriction, called a stenosis. Once so positioned,
the balloon is then expanded in the stenosis by inflating it with
an inflation fluid, to dilate the vessel lumen and facilitate
greater blood flow. Afterwards, the balloon is deflated, and the
catheter is removed from the patient. Examples of such procedures
are coronary angiography and angioplasty, often referred to as
percutaneous transluminal coronary angioplasty (PTCA). Of course,
the present invention may be utilized in any application to which
it is suitable.
Generally, balloon catheters are constructed of a flexible shaft, a
hub affixed to a proximal end of the shaft, and a small inflatable
balloon, usually located at or near a distal tip of the catheter
shaft. The balloon can be inflated by supplying a pressurized
inflation fluid through an inflation port on the hub, which
communicates with an inflation lumen defined by the catheter shaft,
enabling the inflation fluid to flow through a distal end of the
inflation lumen into the interior volume of the balloon. The
balloon is often made of a flexible, relatively inelastic material.
This inelastic material is preferably capable of imposing pressures
of several atmospheres to expand the stenosis, without becoming too
large within the vessel. Likewise, the balloon may be deflated so
the catheter can be withdrawn by pulling a partial vacuum on the
inflation fluid at the inflation port.
In operation, the balloon catheter must be advanced along a
specific path, until the balloon is positioned precisely within the
stenosis. Of course, the physician cannot see most of the catheter.
As a result, the physician navigates the catheter along the desired
path by using fluoroscopy, often referred to as an X-ray machine.
To assist the physician in guiding the catheter, portions of the
catheter may be formed of radiopaque materials, which are highly
visible on a fluoroscope. For example, the catheter shaft may
incorporate a plastic formulation loaded with a radiopaque agent or
filler. Likewise, one or more radiopaque metal marker bands may be
affixed to the catheter shaft in various positions, such as inside
the balloon, or at the distal tip.
Prior to beginning the catheterization, a guiding catheter is
advanced through the vascular system until its distal tip is
located at the entrance to the desired smaller branching vessels.
The guiding catheter acts as a conduit through which various
diagnostic or interventional catheters can be advanced. A type of
radiopaque catheter which can be used to make a guiding catheter is
disclosed in U.S. Pat. No. 5,171,232 to Castillo et al., entitled
"Catheter Having Highly Radiopaque, Flexible Tip," the disclosure
of which is hereby incorporated by reference.
In addition, the balloon catheter may be constructed as a "fixed
wire" catheter, in which the distal end of the inner shaft member
is affixed to a distally extending flexible wire. Otherwise, the
balloon catheter may be provided with a guidewire lumen, forming a
sleeve through which a guidewire can be inserted, advanced, and
withdrawn. Guidewires are described in U.S. Pat. No. 4,846,186 to
Box et al., entitled "Flexible Guidewire," the disclosure of which
is hereby incorporated by reference. The guidewire lumen should
have a lubricious inner surface, to facilitate easy movement of the
balloon catheter along the guidewire.
In a balloon catheter, guidewire lumen types may be classified in
two general categories. The first type is referred to as an "over
the wire" balloon catheter arrangement, which means that the
catheter is advanced over a guidewire which passes through a
guidewire lumen extending along the entire length of the catheter
shaft. This type of guidewire lumen traverses from a distal port at
the catheter distal end to a proximal port on the hub. However, it
is often desirable to remove a previously inserted balloon catheter
and exchange it for another, without also removing the guidewire.
One solution to this problem is to construct a balloon catheter
having the second type of guidewire lumen, referred to as a "rapid
exchange" configuration. This configuration includes a relatively
short guidewire lumen, so that a single operator may withdraw and
exchange a first balloon catheter while holding the guidewire in
place by grasping a portion of the guidewire that is outside of and
parallel to the proximal catheter shaft. A second rapid exchange
balloon catheter can then be advanced over the guidewire in a
similar manner.
There are also two general categories of balloon catheter shafts.
The first type defines the inflation lumen and guidewire lumen in a
side by side and parallel arrangement, often referred to as a "dual
lumen" catheter. This type of shaft is usually formed by a single
tubular extrusion. In contrast, the inflation lumen and guidewire
lumen are arranged coaxially in the second type of catheter shaft,
often called a "coaxial lumen" catheter. In a coaxial lumen
catheter, the balloon guidewire is threaded down the inner passage,
which forms the guidewire lumen, and the inflation fluid is
injected into the balloon via an outer annular passage defined
between the outer surface of an inner guidewire tube and an inner
surface of an outer tube, which forms the inflation lumen.
The balloon itself is often formed having a central cylindrical
portion between a pair of tapering segments. The central portion
has a diameter that is carefully selected to match the size of the
body vessel. The central portion also defines an effective or
working length, and it is desirable to fluoroscopically indicate
the precise location of this working length.
A common feature used to give some indication of the balloon's
position is a marker band in the center of the balloon working
length. Marker bands are made of a radiopaque material such as
platinum. The marker band is then assembled on the catheter by
slipping it onto the inner shaft member and affixing it in position
with an adhesive or by slightly heating the plastic inner
shaft.
Since it is desirable to more accurately indicate the position of
the effective portion of the balloon in the patient's body, the
position of the working length is preferably indicated by a pair of
separate marker bands. Referring to the drawings, the prior art
balloon catheter 200 shown in FIG. 5 has a balloon 202, an inner
and outer shaft member 204 and 206, and a proximal and distal
marker band 208 and 210. The balloon 202 and outer shaft 206 are
each manufactured separately. Likewise, inner shaft member 204 is
also made separately, and marker bands 208 and 210 are affixed to
the inner shaft 204 in isolation from the other components, thus
forming an inner shaft subassembly 212. The marker bands 208 and
210 are thus both permanently affixed to the same inner shaft 204
before the remainder of the balloon catheter 200 is assembled.
However, in the balloon catheter 200 illustrated in FIG. 5, marker
bands 208 and 210 have been affixed to the inner shaft member 204
such that they fail to match with the proximal and distal ends 214
and 216 of the balloon working length 218. There are several
possible reasons for such a mismatch, including the tolerances on
the positions of both marker bands 208 and 210 and the tolerance on
the balloon working length 218. The process for blowing and forming
the balloon 202, including heat treatments of the balloon 202, can
slightly alter its length.
It should be apparent that the elements of catheter 200 shown in
FIG. 5, namely the balloon 202, outer shaft 206, and inner shaft
subassembly 212, cannot be assembled so that both marker bands 208
and 210 are aligned with the ends 214 and 216 of the working length
218. Only one of the marker bands 208 and 210 can be positioned
correctly, but the other will not match. Because of this
misalignment, the particular balloon catheter 200 shown in FIG. 5
would be scrapped. In fact, it is so important that the marker
bands 208 and 210 be exactly positioned, that the tolerance for the
proximal and distal marker band locations can be as narrow as
+/-0.0025 inches.
It is therefore desirable to be able to customize the relative
positions of the markers during assembly, so as to precisely align
them longitudinally with the ends of the balloon working length,
thereby increasing yields during manufacture. Because it is not
feasible to individually tailor the positions of two markers after
they have been affixed to a single shaft member, an unacceptable
percentage of balloon catheters may need to be scrapped if the
markers fail to exactly match both ends of the balloon working
length. In other words, an operator may assemble a balloon onto a
catheter shaft, only to discover that either one marker, but not
both, can properly be aligned with the balloon.
In accordance with the novel balloon catheter design of the present
invention, an intravascular balloon catheter is provided having an
improved arrangement of dual markers to precisely indicate the
balloon working length. This unique arrangement enables the
relative positions of the proximal and distal markers to be
customized during assembly, to exactly match the balloon working
length. In other words, the method and apparatus of the present
invention compensates for the tolerances on the various components.
According to a preferred embodiment of the present invention, a
proximal marker is affixed to a distal end of an outer shaft tube
of a balloon catheter shaft, rather than an inner shaft member. In
contrast, a distal marker is affixed to the inner shaft member,
near its distal end. As a result, the relative positions of the
markers can be adjusted and customized to the exact working length
of a particular balloon by adjusting the longitudinal positions of
the inner and outer shafts.
This precise alignment results from assembling the balloon catheter
according to the method of the present invention. First, the
proximal and distal radiopaque markers are affixed to the outer and
inner shaft members, respectively. Second, the proximal end of the
balloon is then sealed to the outer shaft member, while the
proximal marker and the proximal transition are aligned. Third, the
inner shaft member is inserted within the tubular outer shaft, and
the distal marker affixed to the inner shaft is aligned with the
distal end of the balloon working length. Fourth, the balloon
distal end is sealed to the inner shaft member, such that the
distal marker is longitudinally aligned with the distal end of the
balloon working length. As a result, the position of both markers
is easily adjusted to match the actual balloon working length.
These and various other objects, advantages and features of the
invention will become apparent from the following description and
claims, when considered in conjunction with the appended
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partial cross-sectional view of a balloon catheter
arranged according to the principles of the present invention;
FIG. 2 is a partial cross-sectional view of another balloon
catheter according to this invention;
FIG. 3 is a diagrammatic view of a balloon catheter system
assembled in accordance with this invention, in use within the body
of a patient;
FIG. 4 is a perspective view of a balloon catheter system according
to this invention, showing a partial cross-section of the patient's
vascular system;
FIG. 5 is a partial cross-sectional view of a balloon catheter
according to the prior art;
FIGS. 6-9 are partial cross-sectional views of alternative
embodiments of the present invention;
FIG. 10 is a partial cross-sectional view of another alternative
embodiment of this invention, showing a stent crimped around a
deflated balloon; and
FIGS. 11-14 are partial cross-sectional views of component parts
and subassemblies of a balloon catheter during a method of
manufacturing a balloon catheter according to this invention.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
The following description of the preferred embodiments of the
present invention is merely illustrative in nature, and as such it
does not limit in any way the present invention, its application,
or uses. Numerous modifications may be made by those skilled in the
art without departing from the true spirit and scope of the
invention.
With reference to the drawings, the balloon catheter of the present
invention is generally designated by reference numeral 10. Balloon
catheter 10 has a hub 12, a catheter shaft 14 constructed of an
outer shaft member 16 and an inner shaft member 18, and a
dilatation balloon 20. The hub 12 is affixed to the proximal end 22
of balloon catheter 10, while the balloon 20 is near the catheter
distal end 24. Balloon 20 is preferably formed of a flexible,
substantially inelastic material and defines a predetermined
working length 26 and inflated diameter 28. These dimensions are
used by physicians to carefully select a balloon having the proper
size and effective length for each patient's anatomy.
The balloon 20 preferably has a central working portion 30, a
proximal and distal frusto-conical or tapering segment 32 and 34,
and a proximal and distal leg 36 and 38. A proximal and distal
transition point 40 and 42 are each defined where the central
working portion 30 meets the proximal and distal tapering segments
32 and 34, respectively. The transitions 40 and 42 define the
proximal and distal ends of the balloon working length 26. The
proximal and distal legs 36 and 38 are sealed to the outer and
inner shaft member 16 and 18, respectively, preferably by heat
sealing.
According to the preferred embodiment, the outer and inner shaft
members 16 and 18 are both tubes, as illustrated in FIGS. 1 and 2.
An inflation lumen 44 is defined by a generally annular space
between the inner and outer surfaces 46 and 48 of the outer and
inner shaft members 16 and 18, respectively. Inner shaft member 16
defines a guidewire lumen 50 for slidingly receiving a guidewire
52. The guidewire 52 is used in conjunction with the balloon
catheter 10 to assist in steering and navigating the balloon
catheter 10 along the desired vascular path, so that the balloon 20
reaches the diseased location. The outer surface of outer tube 16
may of course be treated or coated to improve the performance of
the balloon catheter 10, such as by applying a hydrophillic or
other type of coating.
Hub 12 is a Y-connector having an inflation port 54 in fluid
communication with inflation lumen 44, and a guidewire port 56
communicating in conventional manner with guidewire lumen 50.
Inflation port 54 is adapted to be connected by a luer-lock
coupling with a source of pressurized inflation fluid, such as
syringe 58. Inflation lumen 44 extends from inflation port 54 along
the catheter between catheter tubes 16 and 18, and terminates in
communication with the interior of balloon 20. Guidewire port 56
has a hemostatic valve 60 through which the guidewire 52 can pass,
without allowing blood to leak from hub 12. Hub 12 preferably has a
tubular strain relief 62 to resist kinking by the catheter shaft 14
at its proximal end 22. Preferably, hub 12 can be made by
injection-molding it around catheter shaft 14.
Balloon catheter 10 is illustrated in use within the vasculature of
a patient in FIGS. 3 and 4, with a guidewire 52, syringe 58, and a
guiding catheter 64. Balloon 20 is disposed within a stenosis 66,
which will be expanded as balloon 20 inflates. Since the balloon
catheter 20 can be successfully used without surgery, the physician
never sees the cross-sectional view of FIG. 4. Rather, the
physician must rely on a murky fluoroscope image. It is very
important that the physician be able to discern from that image,
exactly where the effective balloon length is located in the
patients body.
In accordance with the present invention, balloon catheter 10
incorporates a novel arrangement of a pair of radiopaque markers
for precisely indicating the location of the balloon working length
26. The markers are disposed within the interior of the balloon 20,
and are positioned along the longitudinal axis of the balloon at
the exact position of the proximal and distal transitions. As shown
in the embodiment of FIG. 1, this unique arrangement enables the
relative positions of proximal and distal markers 68 and 70 to be
customized during assembly of the balloon catheter 10. The present
invention thereby compensates for any variances in component
dimensions or manufacturing tolerances present in the components.
Accordingly, the distal marker 70 is affixed to the inner shaft 18,
yet the proximal marker 68 is affixed to the outer shaft 16. This
enables the distance between the two markers 68 and 70 to be
adjusted to precisely match the working length 26 of a particular
balloon 20.
Balloon catheter 10 is assembled by the method of the present
invention, as illustrated in FIGS. 11-14. Inner shaft 18 is
extruded in the form of a tube, and distal marker band 70 is
affixed to inner shaft 18 near its distal end 24, to form inner
shaft subassembly 72. The position of distal marker band 70 is
selected appropriate to the approximate dimensions of the type of
balloon 20 to be used, and is preferably spaced from the inner
shaft distal end 24 a distance approximately equal to the
longitudinal length of distal balloon tapering segment 34, plus the
length of distal leg 38, plus any desired length of inner shaft
distal tip 74. Also, outer tubular shaft 16 is extruded in the form
of another tube having a larger diameter than inner shaft 18, and
proximal marker 68 is affixed to outer shaft 16 preferably at its
distal end, forming outer shaft subassembly 76. Balloon 20 is
formed according to conventional processes, including for example,
those disclosed in U.S. Pat. No. 5,304,197 to Pinchuk et al.,
entitled "Balloon For Medical Devices And Fabrication Thereof," the
disclosure of which is hereby incorporated by reference. Of course,
balloon 20 as well as inner and outer shaft subassemblies 72 and 76
may be manufactured simultaneously or in whatever desired order, or
even in separate facilities.
Then, a balloon catheter 10 is assembled of a particular balloon 20
with a particular inner and outer shaft subassembly 72 and 76.
These subassemblies 72 and 76 are brought together for the first
time at this stage, and it is not practicable to do so earlier. In
addition, it is not practicable to attempt to precisely place a
pair of markers 68 and 70 on an inner shaft 18 to match the working
length 26 of a specific actual balloon 20, and too expensive then
to keep that particular balloon 20 together with that inner shaft
18 as the subassemblies 72 and 76 are transported to the final
assembly area.
According to the present invention, balloon catheter 10 has a
proximal marker 68 affixed to a distal end of outer shaft 16,
instead of inner shaft 18. As a result, proximal marker 68 may be
precisely aligned to match the proximal balloon transition 40, by
shifting the relative positions of inner and outer shafts 18 and 16
before sealing balloon 20 thereto. In contrast with the prior art
balloon catheter 200 illustrated in FIG. 5, outer shaft tube 16
extends further distally within the interior of the balloon 20. Of
course, outer shaft 16 preferably extends distally just enough to
align the proximal marker 68 in the correct position, to enhance
the flexibility of the distal end of the catheter 10.
Various arrangements of the present invention are possible.
According to the present invention, proximal marker 68 may be made
as a plastic formulation incorporating a radiopaque filler agent,
as illustrated in FIG. 1. Such a marker 68 has several advantages,
among which is that it is flexible. Indeed, proximal marker 68 can
be made even more flexible than outer and inner shaft members 16
and 18, so as to be less traumatic when advanced through
vasculature. Moreover, the percentage of radiopaque filler in the
plastic formulation of proximal marker 68 can be tailored to a
desired degree of radiopacity. Preferably, the radiopacity of
proximal marker 68 may be selected so that the proximal and distal
markers 68 and 70 are equally bright when viewed on a fluoroscope.
Without this tailoring capability, the proximal marker 68 might
appear brighter on the fluoroscope than distal marker 70, because
it has a larger diameter and correspondingly larger size.
In the alternative, the proximal marker may be a metal marker band
78 affixed to outer tubular shaft 16, as depicted in the balloon
catheter 80 FIG. 2. Further, proximal metal marker band 78 may be
disposed around the outside of outer tube, as illustrated in FIG.
2, or a metal proximal marker band 82 may be inserted within the
lumen of outer tube 16, as shown in FIG. 8. Such an interior marker
band configuration exhibits a smoother exterior surface, and may
reduce the profile of the balloon catheter 84.
On the other hand, an exterior marker band 78 may be used to create
a larger proximal shelf or annular surface, which may assist in
advancing a stent 86 crimped over a deflated balloon 88, as shown
in FIG. 10. This type of arrangement will resist a possible
tendency of the stent 86 to slip in a proximal direction while the
balloon catheter 80 is advanced to the desired position within a
lesion or stenosis 66.
In addition, it is often desirable to exchange a first balloon
catheter that has been advanced over a guidewire 52 with a second
balloon catheter, without dislodging the guidewire 52 from the
treatment site. Accordingly, a balloon catheter 90 may be
constructed in a rapid exchange configuration as illustrated in
FIG. 6, wherein a guidewire lumen 92 extends from the distal tip of
the catheter 90 only to a guidewire port 94 between the balloon 96
and the proximal end of the catheter 90. The guidewire 52 then
extends proximally from the guidewire port 94, parallel and
external to the catheter shaft 98.
Alternatively, a balloon catheter 100 of the present invention may
also be provided with "dual lumen" proximal shaft 102 as shown in
FIG. 7, such that proximal shaft 102 is formed of a single
extrusion defining both a proximal guidewire lumen 104 and a
proximal inflation lumen 106, connected with inner and outer distal
tubes 108 and 110 defining a distal guidewire lumen 112 and a
distal inflation lumen 114, respectively.
Referring to FIG. 8, another embodiment of an intravascular balloon
catheter 84 in accordance with this invention is disclosed. The
balloon catheter inner shaft 118 may be constructed of multiple
layers of plastic materials, such as by coextrusion or other
extrusion processes. Similar processes are described in U.S. Pat.
No. 5,063,018 to Fontirroche, which is commonly assigned with the
present application, the disclosure of which is incorporated herein
by reference. In accordance with the present invention, that
extrusion process may be modified to coextrude inner shaft 118.
Tube 118 is formed of an inner layer 120 plus an outer layer 122
which may be added by coextrusion, typically defining a lumen 124
through which a guidewire 52 may be inserted.
Likewise, the balloon 126 of the present balloon catheter 84 may be
constructed of multiple layers 128 and 130, such as in FIG. 8. Such
a multiple layer balloon 126 is disclosed in U.S. Pat. No.
5,290,306 to Trotta et al., entitled "Puncture Resistant Balloon
Catheter," to Trotta, which is commonly assigned and incorporated
herein by reference.
A fixed wire embodiment of the present invention is shown in FIG.
9, in which a balloon catheter 132 includes an inner shaft 134
defining no guidewire lumen. Rather, the inner shaft 134 is firmly
affixed to a flexible wire 136 at the distal end of balloon
catheter 132.
It should be understood that an unlimited number of configurations
for the present invention can be realized. The foregoing discussion
describes merely exemplary embodiments illustrating the principles
of the present invention, the scope of which is recited in the
following claims. Those skilled in the art will readily recognize
from the description, claims, and drawings that numerous changes
and modifications can be made without departing from the spirit and
scope of the invention.
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